Ya the new ones are all variable vane but many old diesels never ran them, A diesel will run with any amount of air surplus.

 

That is another good info link. I was thinking about it this morning but I ran out of time before I left for work.

Rick

 

They do. The older ones have one hooked right to the turbo, pretty basic. And the newer ones use what is called a VGT. Its means variable geometery turbo. It is controled by the ECM. They have a plate in side them over the exducer wheel and control the wheel pitch. This plate in general is controlled by an electronic motor. It has many benifits, quicker warm up tiomes (emissions thing) better response, can be used as an engine brake. I work on them daily so if you want more info just ask.

 

Since diesels rune insane compression anyway, overboosting one of them is not easy to do. Diesel turbos with no wastegate are called free floating turbos; on a diesel, more airflow means more power, simple as that (as long as the fuel system can keep up). Newer diesels use wastegates primarily for getting better gas mileage. The less power it is making, and therefore the less air it is consuming, the better mileage it will get.

It gets quite a bit deeper than that, but I won't go into it...I've been hanging out with a buddy who is a diesel mechanic and have been learning tons